abstract class Shape {
    abstract void getData();

    public static void main(String[] args) {
        Shape cricle=new Circle();
        cricle.getData();

        Shape angle=new RectAngle();
        angle.getData();
    }
}
class Circle extends Shape {

    @Override
    void getData() {
        System.out.println("计算园的面积");
    }
}
class RectAngle extends Shape {

    @Override
    void getData() {
        System.out.println("计算三角的面积");
    }
}
